From 2c0d73ab497cfbafdfdebac5403047751f30fb39 Mon Sep 17 00:00:00 2001
From: Wim Taymans <wtaymans@redhat.com>
Date: Fri, 15 Mar 2024 17:31:43 +0100
Subject: [PATCH] gst: handle latency in the pipewiresrc

Get the delay in the graph and subtract this from the cycle start time
to get the timestamp of the buffer.

Report this latency as well.

Fixes #30
---
 src/gst/gstpipewiresrc.c | 26 ++++++++++++++++----------
 src/gst/gstpipewiresrc.h |  1 +
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/src/gst/gstpipewiresrc.c b/src/gst/gstpipewiresrc.c
index 40c469da3..3aaf2e0b2 100644
--- a/src/gst/gstpipewiresrc.c
+++ b/src/gst/gstpipewiresrc.c
@@ -441,6 +441,8 @@ gst_pipewire_src_init (GstPipeWireSrc * src)
   src->resend_last = DEFAULT_RESEND_LAST;
   src->keepalive_time = DEFAULT_KEEPALIVE_TIME;
   src->autoconnect = DEFAULT_AUTOCONNECT;
+  src->min_latency = 0;
+  src->max_latency = GST_CLOCK_TIME_NONE;
 
   src->client_name = g_strdup(pw_get_client_name ());
 
@@ -549,6 +551,7 @@ static GstBuffer *dequeue_buffer(GstPipeWireSrc *pwsrc)
   struct spa_meta_header *h;
   struct spa_meta_region *crop;
   struct spa_meta_videotransform *videotransform;
+  struct pw_time time;
   guint i;
 
   b = pw_stream_dequeue_buffer (pwsrc->stream);
@@ -567,6 +570,17 @@ static GstBuffer *dequeue_buffer(GstPipeWireSrc *pwsrc)
     return NULL;
   }
 
+  pw_stream_get_time_n(pwsrc->stream, &time, sizeof(time));
+
+  if (pwsrc->delay != time.delay && time.rate.denom != 0) {
+    pwsrc->min_latency = time.delay * GST_SECOND * time.rate.num / time.rate.denom;
+    GST_LOG_OBJECT (pwsrc, "latency changed %"PRIi64" -> %"PRIi64" %"PRIu64,
+		    pwsrc->delay, time.delay, pwsrc->min_latency);
+    pwsrc->delay = time.delay;
+    gst_element_post_message (GST_ELEMENT_CAST (pwsrc),
+      gst_message_new_latency (GST_OBJECT_CAST (pwsrc)));
+  }
+
   GST_LOG_OBJECT (pwsrc, "got new buffer %p", data->buf);
 
   buf = gst_buffer_new ();
@@ -586,8 +600,8 @@ static GstBuffer *dequeue_buffer(GstPipeWireSrc *pwsrc)
     }
     GST_BUFFER_OFFSET (buf) = h->seq;
   } else {
-    GST_BUFFER_PTS (buf) = b->time;
-    GST_BUFFER_DTS (buf) = b->time;
+    GST_BUFFER_PTS (buf) = b->time - pwsrc->delay;
+    GST_BUFFER_DTS (buf) = b->time - pwsrc->delay;
   }
   crop = data->crop;
   if (crop) {
@@ -704,12 +718,6 @@ parse_stream_properties (GstPipeWireSrc *pwsrc, const struct pw_properties *prop
   GST_OBJECT_LOCK (pwsrc);
   var = pw_properties_get (props, PW_KEY_STREAM_IS_LIVE);
   is_live = pwsrc->is_live = var ? pw_properties_parse_bool(var) : TRUE;
-
-  var = pw_properties_get (props, PW_KEY_STREAM_LATENCY_MIN);
-  pwsrc->min_latency = var ? (GstClockTime) atoi (var) : 0;
-
-  var = pw_properties_get (props, PW_KEY_STREAM_LATENCY_MAX);
-  pwsrc->max_latency = var ? (GstClockTime) atoi (var) : GST_CLOCK_TIME_NONE;
   GST_OBJECT_UNLOCK (pwsrc);
 
   GST_DEBUG_OBJECT (pwsrc, "live %d", is_live);
@@ -1171,8 +1179,6 @@ gst_pipewire_src_query (GstBaseSrc * src, GstQuery * query)
   switch (GST_QUERY_TYPE (query)) {
     case GST_QUERY_LATENCY:
       GST_OBJECT_LOCK (pwsrc);
-      pwsrc->min_latency = 10000000;
-      pwsrc->max_latency = GST_CLOCK_TIME_NONE;
       gst_query_set_latency (query, pwsrc->is_live, pwsrc->min_latency, pwsrc->max_latency);
       GST_OBJECT_UNLOCK (pwsrc);
       res = TRUE;
diff --git a/src/gst/gstpipewiresrc.h b/src/gst/gstpipewiresrc.h
index 0a61853f5..ddfef421d 100644
--- a/src/gst/gstpipewiresrc.h
+++ b/src/gst/gstpipewiresrc.h
@@ -68,6 +68,7 @@ struct _GstPipeWireSrc {
   gboolean eos;
 
   gboolean is_live;
+  int64_t delay;
   GstClockTime min_latency;
   GstClockTime max_latency;